1. Field of the Invention
The present invention relates to a magnetic recording apparatus such as a floppy disk unit.
2. Description of the Related Art
Due to a demand for high-density recording, a magnetic head of an preerase system is proposed in a magnetic recording apparatus such as a floppy disk unit. In the magnetic head of this system, an erase head having a large gap length is located at a position preceding a read/write head in a running direction of a disk serving as a magnetic recording medium. As a result, data is erased by the erase head before data is recorded by the read/write head, thereby ensuring compatibility of read/write operation for the disk. In conventional magnetic recording apparatuses using the above-described pre-erase system or the tunnel erase system, a constant erase current is supplied to an erase head to erase data written on a disk.
Magnetic recording media used in a magnetic recording apparatus vary in type depending on differences in recording density and the like. For example, .gamma.-Fe.sub.2 O.sub.3 coating type, Co-.gamma.-Fe.sub.2 O.sub.3 coating type, Ba-ferrite coating type, metal powder coating type, and Co-Cr sputtering type media are used. They are magnetic materials having different coercive forces, and have been developed to increase a recording density or are under development. If coercive forces differ, optimal erase currents also differ.
In order to erase data written on a disk using a magnetic material with a large coercive force, a large erase current may be allowed to flow. However, if a large current value is applied to a disk using a magnetic material having a small coercive force, a problem as shown in FIG. 1 is posed. More specifically, a leaking magnetic flux from an erase gap of an erase head detours to a read/write (R/W) head, and hence a recording waveform tends to be distorted. As recording density is increased, which is a recent trend, distance L between the gaps is decreased. Therefore, if an erase current is set in accordance with a disk having a high recording density, a leaking magnetic flux tends to detour to the read/write (R/W) head when a disk having a low recording density is used. Distortion of a recording waveform is noticeable particularly in a disk having a small coercive force. If the value of an erase current is decreased in order to prevent this problem, data written on a disk having a high recording density cannot be satisfactorily erased.
As described above, in the conventional magnetic recording apparatus with a constant erase current, perfect erasure cannot be expected. In order to perform perfect erasure, an erase current to be supplied to an erase head must be changed in accordance with a type of magnetic recording medium.